ruby-on-rails - 无法通过救援捕获 ActiveRecord::RecordNotFound

Question

我是 Ruby 新手，如果这是一个愚蠢的问题，或者我没有遵循最佳实践，请耐心等待。

我正在使用 find() 在数据库中查找一个对象，并期望它在 id 的对象不存在的情况下抛出 RecordNotFound ，如下所示.

  begin
    event = Event.find(event_id)
  rescue ActiveRecord::RecordNotFound => e
    Rails.logger.debug "Event does not exist, id: " + event_id
    return {
        # return "unauthorized" to avoid testing existence of event id
        # (some redacted codes)
    }
  end 

但不知何故它没有被捕获(救援 block 中的日志没有打印)并且整个程序只是返回内部服务器错误。这是堆栈跟踪:

Completed 500 Internal Server Error in 22ms (ActiveRecord: 1.0ms)



ActiveRecord::RecordNotFound (Couldn't find Event with 'id'=999):

lib/sync/create_update_event_handler.rb:78:in `handleRequest'
app/controllers/sync_controller.rb:36:in `block in sync'
app/controllers/sync_controller.rb:31:in `each'
app/controllers/sync_controller.rb:31:in `sync'
  Rendering /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout
  Rendering /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_source.html.erb
  Rendered /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_source.html.erb (6.4ms)
  Rendering /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb
  Rendered /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_trace.html.erb (2.3ms)
  Rendering /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb
  Rendered /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/_request_and_response.html.erb (1.9ms)
  Rendered /usr/local/rvm/gems/ruby-2.4.0/gems/actionpack-5.0.6/lib/action_dispatch/middleware/templates/rescues/diagnostics.html.erb within rescues/layout (36.6ms)

我唯一能想到的是有两个不同的 ActiveRecord::RecordNotFound，并且我捕获了错误的一个，但我不知道是否是这种情况或如何验证它。 我做错了什么？

========================================

更新

问题出在救援 block 中，我将 event_id (整数)连接到字符串。 RecordNotFound异常确实被捕获，但是当rescue block 中抛出类型错误时，打印了错误的错误消息。

Answer 1

如果这样做，您将不会收到错误

event = Event.find_by(id: event_id)

在这种情况下，如果无法通过 ID 找到记录，则 event == nil 将为 nil。 在这种情况下，如果无法通过 ID 找到记录，则 event == nil 将为 nil。

您粘贴的代码对我来说效果很好。如果您在日志中没有看到输出，请检查您的环境和日志级别设置 INFO、WARN、DEBUG 等。500 错误表示某种 Controller 操作引发了错误。

参见Set logging levels in Ruby on Rails

为了确保您的救援 block 正在执行，请尝试执行除日志之外的其他操作。如果您正在运行开发服务器，您可以尝试:

    begin
         event = Event.find(event_id)
     rescue ActiveRecord::RecordNotFound => e
         msg = "Event does not exist, id: #{event_id.to_s}"
         Rails.logger.debug msg.
         puts msg 
         binding.pry # if you have gem 'pry' in your development gems.
         File.open('test.log', 'w') {|f| f.write msg} #check if this appears in root of your app
         return {
                 # return "unauthorized" to avoid testing existence of event id
                 # (some redacted codes)
         }
     end 

更新:我根据您的回答更改了字符串插值。您还可以在插值内调用 .to_s，而不是关闭引号和附加。